In Wednesday’s Senate Intelligence Committee hearing, Dorsey said he is a man of “few words.” It was a stark contrast to Sandberg, who is more at ease speaking in public; her Washington experience as Larry Summers’ chief of staff at Treasury two decades ago also showed through. But she sounded more like a politician, repeatedly saying “we can do better” and using jargon like “inauthentic accounts.”

Dorsey gave a more honest analysis of the existential dilemma facing his $25 billion micro-blogging site and other social-media platforms – from toxic interactions between users, to promulgation of actual fake news to election meddling.

Yet inflammatory content often produces more user engagement, leading to growth and advertising revenue. Nonetheless, Dorsey told lawmakers he is taking a fundamental look at Twitter’s business model and user incentives. For example, the company is examining whether it’s right to entice a user to gather more followers by putting that figure in a noticeable font. The same goes for retweets. Dorsey said those metrics should not be a proxy for how much a user contributes to healthy dialogue on Twitter, one of the goals of the platform.

The company has already taken action against spam and fake accounts that contravene such ideals. As a result, Twitter’s monthly active users already shrank by 1 million in the second quarter, to 335 million. But his comments to Congress about possible “tectonic” changes sent Twitter shares down by about 5 percent, double Facebook’s decline.

There may be more pain ahead. Democrats are looking at proposals on privacy, legal liability and even antitrust. Republicans, including President Donald Trump, claim anti-conservative bias.

The companies brought the scrutiny on themselves, partly by acting too slowly. But Dorsey sounded humbled and acknowledged reality while Sandberg seemed to think Facebook can manage lawmakers by outtalking them. In an afternoon House hearing, Dorsey said if you sat down with a cup of coffee and read Twitter’s rules, you would not be able to understand them. In the Senate, Sandberg sounded defensive when asked about Facebook’s terms of service.

Dorsey is looking like the industry envoy Silicon Valley needs just as its list of friends is in decline.

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